1. Field of the Invention
The present invention relates to electrolytes in solid capacitors, and more particularly to an electrolyte comprised of TCNQ complex having electron donors with double charges as the major component.
2. Description of the Prior Art
Conventional electrolytic capacitors mostly use electrolytes, however, the need for solid electrolytic capacitors has increased in recent years.
Various compositions of TCNQ complex as the electrolyte of organic semiconductor electrolytic capacitors have been disclosed in U.S. Pat. Nos. 4,982,312, 5,031,077, and 5,766,271. Generally speaking, the TCNQ complex disclosed so far has low melting point, and cannot withstand thermal stress caused in soldering (about 230xc2x0 C.). Consequently, it tends to degrade, creating a noticeable leakage of current. Although a TCNQ complex with high melting point has been disclosed to increase the resistance to heat, after thermal melting and cooling to solidify, the conductivity of TCNQ complex decreases considerably. As a result, excellent high frequency characteristics of TCNQ complex are deducted.
Most conventional research on TCNQ complex is confined to electron donors with a single electric charge. Those TCNQ complex, such as alkyl-iso-quinolinium(TCNQ)2 though widely used, still cannot be used with higher voltages(xcx9c25V). Though there is some discussion of TCNQ complex formed by alkylene-di-lutidinium(TCNQ)4, focus is on its application without sufficient disclosure of TCNQ complex itself. Moreover, the complex disclosed, largely used with high voltages (xcx9c25V) still does not meet requirements.
The object of the present invention is to provide a TCNQ complex formed by salts with double positive charges and TCNQ. The structure of the salt contains functional groups having two electric charge separated by carbon chains of different carbon numbers (normally 21xcx9c16 carbon straight chain, and saturated alkyl or unsaturated ones that is xcfx80 resonance). The functional group having two electric charges can be the same (symmetrical) or different (asymmetrical). The TCNQ complex formed by combining the salts and 2xcx9c4 TCNQ has the following advantages:
1. Excellent conductivity: higher melting point than existing TCNQ complex, and good conductivity maintained even after thermal melting process.
2. Good thermal stability: allows effective control and adjustment to meet specific process requirements. The solid electrolyte created will not degrade in physical properties caused by thermal melting.
3. After thermal/cooling, the melting point increases and the decomposing point remains constant at the second thermal melting.
The synthetic process to prepare the TCNQ complex, shown in the following formula: 
is as follows: 
wherein the electron donors X are quinoline, isoquinoline, lutidine, picoline, pyridine, imidazole, benzoimidazole or their derivatives and combination thereof; l represents leaving group, such as iodine ion, bromine ion, chlorine ion and p-toluenesulfonate etc, and n is a positive integer between 0 and 14; the ratio of TCNQ/electron donor (y) is between 2.5 and 4.0. Optionally, the complex is further comprised of a benzene ring in the carbon chain.
In addition, when used as the electrolyte of a solid capacitor, the double-charge TCNQ complex of the present invention can be mixed with single-charge TCNQ complex.
The present invention will become more fully understood from the preferred embodiments given hereinbelow, given by way of illustration only and thus not intended to be limitative of the present invention.